Why use a loop? Try using diff() x <- c(4, 19, 21, 45, 50, 73, 78, 83, 87, 94) sum(diff(x))
-----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Rafael Moral Sent: Thursday, March 12, 2009 9:04 AM To: r-help@r-project.org Subject: [R] help with loop Dear useRs, I'm trying to write a loop to sum my data in the following way: (the second - the first) + (the third - the second) + (the fourth - the third) + ... for each column. So, I wrote something like this: c <- list() for(i in 1:ncol(mydata)) { for(j in 2:nrow(mydata)) { c[[i]] <- sum(yc[j,i] - yc[(j-1),i]) }}} As for the columns it works pretty fine, but it only returns the last subtraction, however, I need the sum of all subtractions. Any ideas? Regards, Rafael. Veja quais são os assuntos do momento no Yahoo! +Buscados [[alternative HTML version deleted]] =================================== P Please consider the environment before printing this e-mail Cleveland Clinic is ranked one of the top hospitals in America by U.S. News & World Report (2008). Visit us online at http://www.clevelandclinic.org for a complete listing of our services, staff and locations. Confidentiality Note: This message is intended for use\...{{dropped:13}} ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.